1. Technical Field
The invention relates to an image processing device. Particularly, the invention relates to an image processing method, an anti-saturation method for image data and an image processing device using the same.
2. Related Art
FIG. 1 illustrates a conventional image processing device. A global gain generator 110 determines a gain value G according to an operation requirement of the system, and outputs the gain value G to a calculation circuit 120. The calculation circuit 120 receives original image data D1, and calculates a multiplication of the gain value G and the image data D1, and outputs the multiplication (i.e. G*D1) to a display circuit 130 to server as new image data D2. The display circuit 130 drives a display panel to display a corresponding image frame according to the image data D2.
Under a normal operation condition, the global gain generator 110 sets the gain value G to 1. FIG. 2 illustrates a conversion curve between the image data D1 and the image data D2 when the gain value G of FIG. 1 is 1. In FIG. 2, a horizontal axis represents the original image data D1, and a vertical axis represents the new image data D2 converted by the calculation circuit 120. It is assumed that the image data D1 and the image data D2 are all 8-bit data. Under the condition that the gain value G is 1, a value range of the image data D1 is 0-255, and a value range of G*D1 (i.e. the image data D2) is also 0-255.
When the global gain generator 110 sets the gain value G to be greater than 1 (for example, 1.2), the new image data D2 converted by the calculation circuit 120 probably has a phenomenon of saturation. FIG. 3 illustrates a conversion curve between the image data D1 and the image data D2 when the gain value G of FIG. 1 is 1.2. In FIG. 3, a horizontal axis represents the original image data D1, and a vertical axis represents the new image data D2 converted by the calculation circuit 120. It is assumed that the image data D1 and the image data D2 are all 8-bit data. Under the condition that the gain value G is 1.2, a value range of the image data D1 is 0-255, and a value range of G*D1 (i.e. the image data D2) is 0-366. However, since the image data D2 is the 8-bit data, i.e. a maximum value of the image data D2 is 255, when the image data D1 is within a range of 213-255, the image data D2 are all 255, and such phenomenon is the so-called “saturation”. Since the image data D2 has the phenomenon of saturation, details of a high grayscale (high brightness) image frame are disappeared. The greater the gain value G is, the greater the value range having the saturation phenomenon is, and the more severe the detail loss of the high brightness image frame is.